The present invention relates generally to computer graphics and animation, and more particularly to systems and methods for defining rest poses of an animation object.
For fleshy human characters, e.g., human characters in Pixar's WALL●E, an automatic system for secondary ballistic motion is desirable to add an extra level of realism and to lighten the burden on animators. This task can be complicated by the nonphysical nature of the underlying models; the secondary motion should look realistic even if the primary animation is exaggerated and stylized.
During pre-production, the human characters went through several stages of development. Early versions were made of transparent, gelatinous material instead of flesh, and were unrecognizable as humans. This posed interesting problems for animation and simulation. For example, how would one act with a facial performance on a material with no real structure? Also, how would the simulator preserve animation detail and still allow the material to undergo large deformation? As the story evolved the jelly creatures became more human, and the requirements of the simulator changed. Detail preservation grew easier as key details in the face and hands were now adjacent to bones and required less secondary motion, but maintaining animation silhouettes elsewhere in the body became more important.
Typically, a mass-spring system is used to model the internal physics of the material, e.g., skeleton structure of fleshy human characters. With constraint forces alone the large changes in shape between different poses of the character would be constantly fought by the spring forces in the simulation. For example, for sufficient deformations to a rest pose by an animator, the mass-spring system would tend to force the object back to the initial rest pose, thereby creating unrealistic animation.
Therefore it is desirable to provide systems and methods that overcome the above and other problems.